The present invention relates to heat sealable packages wherein the packages are made of multilayer polymeric films. Move particularly, the invention relates to polymeric films which incorporate two peel mechanisms which are temperature dependent.
Packages made of polymeric film having this feature are highly desirable in the packaging industry because they allow the package fabricator greater flexibility in sealing temperatures without compromising the ease in opening the package by the consumer. Background of the Invention The present invention provides easy open, peelable seal packages which are made of multilayer polymeric films and contain a variety of food and non-food products. The packages of the present invention are heat-sealed over a wide range of sealing temperatures to a closed position to contain and to protect the products contained therein. These packages can be opened by application of force at a designated position on the package. Since the multilayer polymeric film which makes up the packages incorporates two peel mechanisms, the packages open via a surface peel or a delamination peel mechanism wherein said mechanism is dependent on sealing temperature.
The technology of peelable seal, easy-open packaging has been employed initially in the food industry with expanding applications over the years into non-food arcs U.S. Pat. No. 4,944,409 issued to Busche and Bostian (the xe2x80x9c409xe2x80x9d patent) discloses an package which is adopted to be heat sealed to a closed position, The subject package includes a first and second package wall. The first wall comprises a thermoplastic polymeric film construction having an outer layer, an inner sealant layer and a tie layer disposed between and cohesively bonded to either the inner layer or the outer layer. The package disclosed in the xe2x80x9c409xe2x80x9d patent has only one seal mechanism. Therefore, a need exists in this area of technology to develop a peelable seal package which has the following features: (1) constructed of polymeric film; (2) employs two peelable seal mechanisms which are dependent on sealing temperature; (3) sealed closed after insertion of product over a wide range of sealant temperatures; and (4) opened by the consumer using an acceptable level of force.
The present invention relates to easy-open, peelable. seal packages which can be sealed closed after insertion of product over a wide range of sealant temperatures and having two peel mechanisms. The packages are typically constructed on form/fill/seal equipment which joins together the sides and bottom of a web of polymeric film to form an open pouch, then inserts the product, and then seals the remaining portion (typically the top) closed.
The packages of the present invention can be opened by the consumer via either of two peel mechanisms; a surface peel mechanism or a delamination peel mechanism.
A surface peel mechanism is that mechanism which operates by failure of the adhesive bond between the interface of layer one of the first package wall with layer one of the second package wall (See FIG. 6 and FIG. 7). A surface peel mechanism operates at sealant temperatures below 210xc2x0 F., preferably between 180xc2x0 F. and 210xc2x0 F.). A delamination peel mechanism is that mechanism which operates by failure of the cohesive bond between layer two and layer one (See FIG. 4 and FIG. 5) with tearing through layer one. A delamination peel mechanism operates at sealant temperature above 210xc2x0 F., (preferably between 210xc2x0 F. to 250xc2x0 F.).
The choice of peel mechanisms will be determined by the sealing temperature. The sealing temperature is that temperature which is employed to seal the package after the insertion of the product. Specifically, the sealing temperature is that temperature used to seal the first layer of the first package wall to the second package wall to create a totally closed package. A sealing temperature range suitable for use in the present invention is between 180xc2x0 F. to 250xc2x0 F.
Generally, the higher the sealing temperature, the higher the amount of force required by the consumer to open the package. Therefore, it becomes important to maintain the sealing temperature at an acceptable range so that a minimum amount of force is required by the consumer to open the package. Also, it is desirable for the fabricator of the totally closed package that a wide range of sealing temperatures be available in order to allow for greater flexibility in the fabrication process (i.e., sealing temperatures do not have to be monitored so closely).
The present invention also relates to a multilayer polymeric film construction comprising two or more layers wherein each layer consists of a single polymeric material or a combination of polymeric material.
In a first preferred embodiment, the invention provides an easy open package adopted to be heat sealed closed over a wide range of sealing temperatures in order to contain and protect the product within the package. The package is easily opened by the application of a manual force along the intersurface of first package wall and the intersurface of the second package wall. The package includes a first package wall having a multilayer film construction. The multilayer film construction includes in one embodiment the following layers: a fifth layer; a fourth layer; a third layer; a second layer comprising high density polyethylene (HDPB) and polybutylene (PB) and a first layer comprising ethylene vinyl acetate copolymer (EVA), plastomer and polybutylene (PB). The package also includes a second package wall joined at a portion of its perimeter to the first package wall. The first layer of first package wall is heat sealed to the second package wall to create a sealed package. The temperature at which the first layer of the first package wall is heat sealed to the first layer of the second package wall to create a sealed package will determine which of the two peel mechanisms will be employed to open the package.
In a second, preferred embodiment, the first package wall has a multilayer film construction specifically including the following layers: a fifth layer comprising high density polyethylene; a fourth layer comprising high density polyethylene; a third layer comprising high density polyethylene; a second layer comprising high density polyethylene and polybutylene and a first layer comprising ethylene vinyl acetate copolymer, polyethylene plastomer and polybutylene such that a controlled cohesive bond is formed either between said second layer and said first layers or, between the first layer of the first package wall and the first layer of the second package wall. The package also includes the second package wall joined at its perimeter to the first package wall, that is part of the same original web of polymeric film.
In a third, preferred embodiment, the first package wall has a multilayer film construction specifically including the following layers, a fifth layer comprising high density polyethylene; a fourth layer comprising a polymer selected from the group consisting of high density polyethylene and linear low density polyethylene, or a blend of high density polyethylene and linear low density polyethylene, a third layer comprising high density polyethylene; a second layer comprising high density polyethylene and polybutylene and a first layer comprising ethylene vinyl acetate copolymer, plastomer and polybutylene such that a controlled cohesive bond is formed either between said second layer and said first layer or between the first layer of the first package wall and the first layer of the second package wall. The package also includes the second package wall joined at its perimeter to the first package wall, that is part of the same original web of polymeric film.
In an especially preferred embodiment, the first layer of either the first package wall or the second package wall or both package walls comprises approximately 20 to 50 percent of ethylene vinyl acetate copolymer with 30 to 40 percent being preferred; approximately 30 to 60 percent of plastomer with 40 to 50 percent being preferred; and approximately 5 to 25 percent of polybutylene with 10 to 20 percent being preferred.
In another embodiment of the present invention, the invention provides a multilayer film construction comprising two layers: a first layer comprising ethylene vinyl acetate copolymer, plastomer and polybutylene which is adjacent to a second layer comprising high density polyethylene and polybutylene. This multilayer film construction can be bonded to one or more other polymeric layers.
In a preferred embodiment of a multilayer film construction comprising two layers: a first and second layer, the first layer comprises approximately 20 to 50 percent of ethylene vinyl acetate copolymer with 30 to 40 percent being preferred; approximately 30 to 60 percent of a plastomer with 40 to 50 percent being preferred; and approximately 5 to 25 percent of polybutylene with 10 to 20 percent being preferred; and the second layer comprises approximately 20 to 80 percent of polyethylene with 40 to 60 percent being preferred and approximately 20 to 80 percent of polybutylene with 40 to 60 percent being preferred.